The invention relates to a roll-down shutter comprising a rotating, self-locking winding shaft having coilable shutter-armor made of linked interconnected shutter elements, whereby the top-most shutter element is attached to the winding shaft.
Various methods are already known for increasing the security of roll-down shutters. One such method consists of a self-locking winding shaft that is provided with a worm drive which is only rotatable by a hand crank or a motor, that can be self-turned by motor cutoff or hand-crank and not by attacking the winding shaft. A suitable formation of the top-most shutter element together with subsequent shutter elements (usually in a shutter box), prevents any unauthorized pushing up of the shutter armor. A previous weakness was the attachment of the top-most shutter element onto the exhaust-shaft, that previously resulted from screwing or bolting. After opening the shutter box, it was thus possible for an intruder with relatively simple tools to loosen the top-most shutter element from the winding shaft thereby pulling the shutter armor away despite the shaft being in the locked position.
The invention seeks to produce a roll-down shutter of a known type which provides greater security.
According to the invention, this is accomplished by binding the top-most shutter element to the winding shaft in a closed-shape.
With close-shaped binding, it is understood in the sense of the invention, that the binding has two structural pieces (here the winding shaft and the top-most shutter element) whereby the cohesion of the two parts is determined through the form of the two interlocking parts so that no additional binding agents such as screws, bolts or the like are necessary.
According to the invention, this closed-shape binding holds the two parts (winding shaft and top-most shutter element) undetachably together, but in contrast to the closed-shape where the parts are correspondingly bound together with essentially no slippage, restricted relative movement of the two parts is permitted. The top most shutter element may not be removed in a radial direction perpendicular to the axis of the winding shaft, but the binding is not completely fixed. It is possible to tilt or pivot the element and to remove it or insert it in an axial direction.
In a preferred embodiment, such a closed-shape binding between the winding shaft and top-most shutter element forms a first binding section in the axial direction on the winding shaft and a second binding section on the top-most shutter element in the axial direction of the shaft. The first binding section is joined to the second binding section to attach the shaft to the top-most shutter element--preferably with some looseness (play). With the assembly of the roll-down shutter, the two binding sections can simply be pushed into one another in axial direction and held together in closed-shape, whereby a removal of the top-most shutter element in any radial direction out of the winding shaft is not possible. Since a radial pushing out of the top-most shutter element is not possible with insertion into the winding shaft and releasable binding agents such as screws, bolts, or similar are not provided, the top-most shutter element cannot be separated from the winding shaft, thus making it impossible for the intruder to pull up the shutter.